Aerial system



y'l'. DOUMA y AERIAL SYSTEM fd-l-/l Filed Jan. ,21, 1942 Patented pr. 4, 1944 l AERIAL SYSTEM Tjiske Douma, Eindhoven, Netherlands; vested in the Alien Property Custodian Application January 21, 194.2, Serial No. 427,599 In the Netherlands July 20, 1940 (Cl. Bll- 33) Claims.

For the transmission or reception of television, as well as for definite systems of altimetry and obstacle detection in which use is made of a high carrierwave frequency, it is necessary to utilize aerial systems which, in contradistinction to a simple dipole aerial, have an impedance of which the absolute value for a frequency range of about 10% of the carrier-wave frequency varies by 10% at most.

For such purposes it is known to utilize a dipole aerial system constituted by two conical metal bodies having their points adjacent one another.

A drawback of this cone aerial is the complicated and voluminous construction which is necessary to obtain a suicient structural rigidity and which renders the aerial system comparatively expensive; moreover, it has a shape which is unsuitable for mounting on an airplane.

The invention has for its object an aerial system of simple and cheap construction which is suitable for the above mentioned purposes.

To this end, in an aerial system comprising at least two radiators arranged adjacent to and parallel with one another, of which the interval therebetween is small relatively to the length of the radiators, while short-circuits are provided between the corresponding extremities of the radiators. Each of the said short-circuits, according to the invention, is so made that it extends over part of the length of the radiators so that, as viewed in the longitudinal direction of the radiators, points of one of the radiators located next to one another and in the proximity of the extremities are connected by it directly to similarly located points of the other of the radiators.

The aerial system according to the invention is preferably utilized at a wavelength which is equal to about double the length of a radiator.

It has been found that, considering the object aimed at, a very advantageous form of the impedance-requency curve of the aerial system is obtained if each of the said short circuits, as viewed in the longitudinal direction of the radiators, extends over a distance larger than 1/0 and smaller than 1/5 of the length of a radiator.

Each of the short-circuits is preferably constituted by a plane metal plate located in or at least substantially in a plane surface defined by two of the radiators.

A particularly advantageous impedance-irequency curve of the aerial system according to the invention is obtained by using two radiators, one of the two radiators being constituted by a metal band whose Width is preferably smaller than the interval of the two radiators, the other of the two radiators being interrupted in the center and connected to a transmission line.

In order that the invention may be more clearly understood and readily carried into effect, it will be explained more fully by reference to the accompanying drawing.

Figure 1 shows a known aerial system for comparison with the aerial system according to the invention.

Figures 2 and 3 show advantageous forms of construction of aerial systems according to the invention.

In Figure 4 the impedance-frequency curves of the aerial systems shown in Figures 1, 2 and 3 are represented for wavelengths corresponding to about double the length of a radiator.

The known aerial system shown in Figure l is constituted by three radiators l, 2 and 3 which are arranged adjacent to and parallel with one another and whose length is substantially equal to half of the wavelength utilized. The central one of the radiators (2) is interrupted in its center and connected to a transmission line 4 which is connected to a suitable transmitter or receiver. Short-circuits 5 are provided between corresponding extremities of the radiators.

As may be assumed as known, the radiators of such an aerial system are excited with equal phase and consequently in the case of resonance of such a three-fold dipole the impedance is about 9 times as great as the resonance' impedance of a simple dipole.

In Figure 4 the absolute value of the impedance of the aerial system of Figure l, as viewed from the transmission line, is represented as a function of frequency by the curve I. It appears therefrom that it greatly varies in the vicinity of the resonance frequency of the aerial which is about 71 megacycles/sec.

The aerial system according to the invention shown in Figure 2, like the aerial system shown in Figure l, is constituted by three radiators 6, l, 8 respectively which are arranged adjacent to and parallel with one another and of Whichthe central one is interrupted and connected to a transmission line 9. Here again the radiators are short-circuited at their extremities, but in contradistinction to the aerial system shown in Figure 1 the short-circuits of the corresponding extremities of the radiators are brought about by plane plates le which are located in the plane surface common to all radiators. Each of these plates brings about a short-circuit which extends over part of the length of the radiators, thus connecting points of one of the radiators located next to one another and in the vicinity of the extremities directly toy similarly located points of the other radiators.

As appears from the impedance-frequency curve Il measured for the aerial system shown in Figure 2, the maximum variation of the aerial impedance, if the carrier-wave frequency of the oscillations to be transmitted or to be received is about 61 megacycles/sec., for a frequency range of about 10% of the carrier-wave frequencies (58-64 megacycles/sec.) is smaller than 8% of the average impedance of the aerial.

A still more advantageous form of the impedance curve of the aerial system according to the invention is obtained with the aid of the aerial system shown in Figure 3 which consists of two radiators. According to this form of construction, the extremities of the two radiators I i and l2 are connected together by metal plates i3' located in the plane surface comprising the two radiators, said connection being elfected over` a distance which is about 1/10 of the length of a radiator, or about 1/20 of the wavelength utilized, as in the form 'of construction shown in Figure 2. However, in this form, the upper one of the two radiators (Il) consists of a metal band whose width is less than the interval between the radiators. The other of the two radiators (l2) is interrupted in its center and connected to the extremities of the transmission line I4.

In Figure 4, III is the impedance-frequency curve of the aerial system shown in Figure 3. It appears therefrom that for a frequency range of more than 10% of the average frequency, viz. 8 megacycles/sec. (5S-64 megacycles/sec.), the maximum variation of the aerial impedance is less than 1%, i. e., that the aerial impedance for practical purposes may be considered las constant.

t may further be remarked that the absolute value of the impedance of the aerial system shown in Figure 3, which consists of two radiators, is approximately equal to that of the aerial system shown in Figure 2 which consists of three radiators. In both casesthis impedance is about 700 ohms, which value is particularly advantageous in View of the adaptation of the impedance of the aerial system to that of the transmission line.

I claim:

l. An aerial system including at least two closely adjacent parallel conductors, the length of said conductors being of the order of a half of the operating wave-length and conductive connecting means between said conductors at each end thereof, said means affording a plurality of parallel paths for radio frequency energy over a substantial part of the length of each conductor.

2. An aerial system including at least two closely adjacent parallel conductors, the length of said conductors being of the order of a half of the operating wave-length and conductive connecting means extending between said conductors at each end thereof, each of said connecting means being in the form of a single plane metallic platel lying inthe plane dened by said conductors.

3'. An aerial system including at least two closely adjacent parallel conductors, the length of said conductors being of the order of :a half of the operating wavelength and connections between said conductors at each end thereof, said connections being in the form of plane metallic plates lying in the plane defined by said conductors, each of said plates extending inwardly along said conductors from the ends thereof a distance which is larger than one-twentieth and smaller than one-fifth of the length of said conductors.

4. An antenna system as set forth in claimr l, wherein one of said conductors is interrupted at its center and connected to one end of a transmission line.

5. An antenna system as set forth in claim 2, wherein one of said conductors is interrupted at its center and connected to one end of a transmission line.

6. An aerial system including at least two closely adjacent parallel conductors, the length of said conductors .being of the order of a half of the operating wavelength, one of said conductors being in the form of a metallic band having a width less than the spacing between said conductors and conductive connecting means between said conductors at each end thereof, said means affording a plurality of parallel paths for radio frequency energy extending over a substantial part of the length of each conductor.

7. An antenna system including a narrow elongated at metallic band having a length substantially equal to half the operating wavelength and an equal length wire arranged .parallel and closely adjacent thereto, said band having end portions which are w-ider than the central portion, said wire being connected to said band along the length of each of said wider portions.

8. An antenna system including a narrow elongated fiat metallic band having a length substantially equal to half the operating wavelength and an equal length wire arranged 4parallel and closely adjacent thereto, said band having end portions which are wider than the central portion, said wire being connected to said band along the length of each of said wider portions, said wire being interrupted at its midpoint and connected to one end of a transmission line.

9. An antenna system including a narrow elongated fiat conductive band having a length substantially equal to half the length of the operating wavelength and an equal length wire arranged parallel and closely adjacent thereto and in the plane of said band, said band having end portions which are wider than the central portion, said wire being connected to said band along the length of each of said wider portions, said wire being interrupted at its midpoint and connected to one end of a transmission line.

l0. An aerial system comprising, a pair of conductive elongated members extending parallel to eachother in close proximity with a predetermined space therebetween, and a pair of conductive plate members positioned at the opposite ends of the conductive members in alignment therewith with the plate 4members bridging the space between the elongated members and having opposite side edges in alignment respectively with the remote sides 0f the' elongated members, whereby the aerial system is a fixed unitary elongated structure the main central portion of which is formed Iby the spaced elongated members and the two end portions of which are formed by the two conductive plates.

TJISKE DOUMA. 

